1. Field of the Invention
Embodiments of the invention generally relate to a ground shield for semiconductor processing chamber.
2. Description of the Related Art
Physical vapor deposition (PVD), or sputtering, is one of the most commonly used processes in the fabrication of electronic devices. PVD is a plasma process performed in a vacuum chamber where a negatively biased target is exposed to a plasma of an inert gas having relatively heavy atoms (e.g., argon (Ar)) or a gas mixture comprising such inert gas. Bombardment of the target by ions of the inert gas results in ejection of atoms of the target material. The ejected atoms accumulate as a deposited film on a substrate placed on a substrate pedestal disposed within the chamber.
A ground shield may be disposed in the chamber to help define a processing region in a desired region within the chamber with respect to the substrate. The ground shield helps confine the plasma within the processing region. Confining the plasma and the ejected atoms to the processing region helps maintain other components in the chamber free from deposited materials and promotes more efficient use of target materials, as a higher percentage of the ejected atoms are deposited on the substrate.
The ground shield (typically attached to the walls, or body, of the vacuum chamber) is electrically coupled to the vacuum chamber walls and is electrically isolated from the target. In addition, a small gap is maintained between the edge of the ground shield and the target to prevent the plasma from forming outside of the processing region. If enough material from the target is deposited on the ground shield during PVD processing, the deposited material may bridge the gap and the electrical isolation between the ground shield and target will be lost. The loss of electrical isolation will disrupt processing.
Therefore, there is a need in the art for an improved ground shield for use in a PVD chamber.